1. Field of the Invention
The present invention relates in general to a vehicle control apparatus adapted to control an engine during a shifting action of an automatic transmission which is arranged to receive an output of the engine, or during a switching of an operating state of a lock-up clutch provided in a fluid-operated transmitting device interposed between the engine and the automatic transmission. More particularly, the present invention is concerned with techniques for controlling a torque transmitted to the automatic transmission during the shifting action of the automatic transmission or during the switching of the operating state of the lock-up clutch.
2. Discussion of the Related Art
There is known a vehicle control apparatus for an automotive vehicle having an automatic transmission and an engine capable of controlling or changing its rotational speed thereof by itself. The control apparatus is adapted to temporarily reduce an output torque of the engine during a shifting action of the automatic transmission which receives the output torque from the engine, for the purpose of reducing a shifting shock of the automatic transmission. That is, during a shift-up action of the automatic transmission, the output torque of the engine is reduced temporarily in an inertia phase. During a shift-down action of the automatic transmission, the output torque of the engine is reduced temporarily upon completion of the shift-down action of the automatic transmission. An example of such a control apparatus is disclosed in JP-A-2001-182820 (publication of unexamined Japanese Patent Application laid open in 2001). Another example of the control apparatus is disclosed in JP-A-H11-36909 (publication of unexamined Japanese Patent Application laid open in 1999), wherein the output torque of the engine is temporarily reduced in the process of the shift-up action by retarding an ignition timing of the engine as shown in FIG. 14 of the publication.
However, in the conventional control apparatuses, the shifting shock of the transmission is not necessarily reduced to a sufficiently small degree, due to restrictions or limitations in an amount of the reduction of the engine output torque and also in the timing at which the output torque is to be reduced. For example, where the output torque is intended to be temporarily reduced by retarding of an ignition timing of the engine, the ignition timing can not be retarded by such a large extent that would overload a catalytic converter of the vehicle. Thus, such a restriction or limitation makes it impossible to sufficiently reduce the engine output torque and the shifting shock.